How to gain muscle without any tools?

Diet and muscle mass: To gain muscle weight you have to consume enough calories. Do this in a healthy way though. Don't choose junk or fast food. Keep a well balanced diet and make sure you are getting all the nutrients you need. Weight lifting and other muscle building exercises can help you increase one's body mass. Try push-ups, sit-ups, pull-ups, leg-lifts, and other exercises not needing a gym.